Unveiling the promoting mechanism of Mo on the performance of CuCeO_x catalyst for simultaneously NH₃-SCR denitration and CO oxidation under oxygen-rich conditions

NO_x and CO coexisted in numerous actual industrial flue gases. The simultaneous removal of NO_x and CO had great potential for application but remained still a challenge. Herein, a series of Mo-modified CuCeO_x catalyst was developed to simultaneously achieve NH₃-SCR denitration and CO oxidation. The results indicated that the CCM3 catalyst displayed the optimal performance with 91.2 % NO_x conversion and 100 % CO conversion as well as excellent long-time stability and SO₂ or/and H₂O tolerance at 225 ℃. It was found that the strong interaction between Cu, Ce and Mo oxides resulted in the particles highly dispersed with smaller size on catalyst surface, which could provide abundant active sites to decreasing the competitive adsorption among reactive gases. Furthermore, the Mo modification promoted the production of more oxygen vacancies, Ce³⁺ and O_α species, which facilitated the redox recycle and the generation of intermediates. Moreover, the H₂-TPR and NH₃/CO/O₂-TPD analysis illustrated that the reducibility and the capacity for reaction gas adsorption and activation were enhanced, which improved low-temperature activity. The in situ DRIFTS experiment revealed that the E-R and L-H mechanism were existed in NH₃-SCR process on CC and CCM3 catalysts. What's more, the stronger acidity and strengthened E-R mechanism on CCM3 catalyst hindered the adsorption of SO₂ and weakened the inhibition effect of competitive adsorption among SO₂ and NO. Additionally, both surface lattice oxygen and chemisorbed oxygen could react with Cu⁺–CO species to produce CO₂, the pathway obeyed L-H and MvK mechanism. This work may provide a novel strategy for the treatment of CO and NO_x pollutants in industrial flue gas.